/*
 * Copyright (c) 2003, 2005, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package javax.xml.xpath;

import org.xml.sax.InputSource;
import javax.xml.namespace.QName;
import javax.xml.namespace.NamespaceContext;

/**
 * <p><code>XPath</code> provides access to the XPath evaluation environment and expressions.</p>
 *
 * <a name="XPath-evaluation"/> <table border="1" cellpadding="2"> <thead> <tr> <th
 * colspan="2">Evaluation of XPath Expressions.</th> </tr> </thead> <tbody> <tr> <td>context</td>
 * <td> If a request is made to evaluate the expression in the absence of a context item, an empty
 * document node will be used for the context. For the purposes of evaluating XPath expressions, a
 * DocumentFragment is treated like a Document node. </td> </tr> <tr> <td>variables</td> <td> If the
 * expression contains a variable reference, its value will be found through the {@link
 * XPathVariableResolver} set with {@link #setXPathVariableResolver(XPathVariableResolver
 * resolver)}. An {@link XPathExpressionException} is raised if the variable resolver is undefined
 * or the resolver returns <code>null</code> for the variable. The value of a variable must be
 * immutable through the course of any single evaluation.</p> </td> </tr> <tr> <td>functions</td>
 * <td> If the expression contains a function reference, the function will be found through the
 * {@link XPathFunctionResolver} set with {@link #setXPathFunctionResolver(XPathFunctionResolver
 * resolver)}. An {@link XPathExpressionException} is raised if the function resolver is undefined
 * or the function resolver returns <code>null</code> for the function.</p> </td> </tr> <tr>
 * <td>QNames</td> <td> QNames in the expression are resolved against the XPath namespace context
 * set with {@link #setNamespaceContext(NamespaceContext nsContext)}. </td> </tr> <tr>
 * <td>result</td> <td> This result of evaluating an expression is converted to an instance of the
 * desired return type. Valid return types are defined in {@link XPathConstants}. Conversion to the
 * return type follows XPath conversion rules.</p> </td> </tr> </table>
 *
 * <p>An XPath object is not thread-safe and not reentrant. In other words, it is the application's
 * responsibility to make sure that one {@link XPath} object is not used from more than one thread
 * at any given time, and while the <code>evaluate</code> method is invoked, applications may not
 * recursively call the <code>evaluate</code> method. <p>
 *
 * @author <a href="Norman.Walsh@Sun.com">Norman Walsh</a>
 * @author <a href="Jeff.Suttor@Sun.com">Jeff Suttor</a>
 * @see <a href="http://www.w3.org/TR/xpath">XML Path Language (XPath) Version 1.0</a>
 * @since 1.5
 */
public interface XPath {

  /**
   * <p>Reset this <code>XPath</code> to its original configuration.</p>
   *
   * <p><code>XPath</code> is reset to the same state as when it was created with {@link
   * XPathFactory#newXPath()}. <code>reset()</code> is designed to allow the reuse of existing
   * <code>XPath</code>s thus saving resources associated with the creation of new
   * <code>XPath</code>s.</p>
   *
   * <p>The reset <code>XPath</code> is not guaranteed to have the same {@link
   * XPathFunctionResolver}, {@link XPathVariableResolver} or {@link NamespaceContext}
   * <code>Object</code>s, e.g. {@link Object#equals(Object obj)}. It is guaranteed to have a
   * functionally equal <code>XPathFunctionResolver</code>, <code>XPathVariableResolver</code> and
   * <code>NamespaceContext</code>.</p>
   */
  public void reset();

  /**
   * <p>Establish a variable resolver.</p>
   *
   * <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> is
   * <code>null</code>.</p>
   *
   * @param resolver Variable resolver.
   * @throws NullPointerException If <code>resolver</code> is <code>null</code>.
   */
  public void setXPathVariableResolver(XPathVariableResolver resolver);

  /**
   * <p>Return the current variable resolver.</p>
   *
   * <p><code>null</code> is returned in no variable resolver is in effect.</p>
   *
   * @return Current variable resolver.
   */
  public XPathVariableResolver getXPathVariableResolver();

  /**
   * <p>Establish a function resolver.</p>
   *
   * <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> is
   * <code>null</code>.</p>
   *
   * @param resolver XPath function resolver.
   * @throws NullPointerException If <code>resolver</code> is <code>null</code>.
   */
  public void setXPathFunctionResolver(XPathFunctionResolver resolver);

  /**
   * <p>Return the current function resolver.</p>
   *
   * <p><code>null</code> is returned in no function resolver is in effect.</p>
   *
   * @return Current function resolver.
   */
  public XPathFunctionResolver getXPathFunctionResolver();

  /**
   * <p>Establish a namespace context.</p>
   *
   * <p>A <code>NullPointerException</code> is thrown if <code>nsContext</code> is
   * <code>null</code>.</p>
   *
   * @param nsContext Namespace context to use.
   * @throws NullPointerException If <code>nsContext</code> is <code>null</code>.
   */
  public void setNamespaceContext(NamespaceContext nsContext);

  /**
   * <p>Return the current namespace context.</p>
   *
   * <p><code>null</code> is returned in no namespace context is in effect.</p>
   *
   * @return Current Namespace context.
   */
  public NamespaceContext getNamespaceContext();

  /**
   * <p>Compile an XPath expression for later evaluation.</p>
   *
   * <p>If <code>expression</code> contains any {@link XPathFunction}s, they must be available via
   * the {@link XPathFunctionResolver}. An {@link XPathExpressionException} will be thrown if the
   * <code>XPathFunction</code> cannot be resovled with the <code>XPathFunctionResolver</code>.</p>
   *
   * <p>If <code>expression</code> contains any variables, the {@link XPathVariableResolver} in
   * effect <strong>at compile time</strong> will be used to resolve them.</p>
   *
   * <p>If <code>expression</code> is <code>null</code>, a <code>NullPointerException</code> is
   * thrown.</p>
   *
   * @param expression The XPath expression.
   * @return Compiled XPath expression.
   * @throws XPathExpressionException If <code>expression</code> cannot be compiled.
   * @throws NullPointerException If <code>expression</code> is <code>null</code>.
   */
  public XPathExpression compile(String expression)
      throws XPathExpressionException;

  /**
   * <p>Evaluate an <code>XPath</code> expression in the specified context and return the result as
   * the specified type.</p>
   *
   * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item
   * evaluation, variable, function and <code>QName</code> resolution and return type
   * conversion.</p>
   *
   * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants} (
   * {@link XPathConstants#NUMBER NUMBER}, {@link XPathConstants#STRING STRING}, {@link
   * XPathConstants#BOOLEAN BOOLEAN}, {@link XPathConstants#NODE NODE} or {@link
   * XPathConstants#NODESET NODESET}) then an <code>IllegalArgumentException</code> is thrown.</p>
   *
   * <p>If a <code>null</code> value is provided for <code>item</code>, an empty document will be
   * used for the context. If <code>expression</code> or <code>returnType</code> is
   * <code>null</code>, then a <code>NullPointerException</code> is thrown.</p>
   *
   * @param expression The XPath expression.
   * @param item The starting context (a node, for example).
   * @param returnType The desired return type.
   * @return Result of evaluating an XPath expression as an <code>Object</code> of
   * <code>returnType</code>.
   * @throws XPathExpressionException If <code>expression</code> cannot be evaluated.
   * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in
   * {@link XPathConstants}.
   * @throws NullPointerException If <code>expression</code> or <code>returnType</code> is
   * <code>null</code>.
   */
  public Object evaluate(String expression, Object item, QName returnType)
      throws XPathExpressionException;

  /**
   * <p>Evaluate an XPath expression in the specified context and return the result as a
   * <code>String</code>.</p>
   *
   * <p>This method calls {@link #evaluate(String expression, Object item, QName returnType)} with a
   * <code>returnType</code> of {@link XPathConstants#STRING}.</p>
   *
   * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item
   * evaluation, variable, function and QName resolution and return type conversion.</p>
   *
   * <p>If a <code>null</code> value is provided for <code>item</code>, an empty document will be
   * used for the context. If <code>expression</code> is <code>null</code>, then a
   * <code>NullPointerException</code> is thrown.</p>
   *
   * @param expression The XPath expression.
   * @param item The starting context (a node, for example).
   * @return The <code>String</code> that is the result of evaluating the expression and converting
   * the result to a <code>String</code>.
   * @throws XPathExpressionException If <code>expression</code> cannot be evaluated.
   * @throws NullPointerException If <code>expression</code> is <code>null</code>.
   */
  public String evaluate(String expression, Object item)
      throws XPathExpressionException;

  /**
   * <p>Evaluate an XPath expression in the context of the specified <code>InputSource</code> and
   * return the result as the specified type.</p>
   *
   * <p>This method builds a data model for the {@link InputSource} and calls {@link
   * #evaluate(String expression, Object item, QName returnType)} on the resulting document
   * object.</p>
   *
   * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item
   * evaluation, variable, function and QName resolution and return type conversion.</p>
   *
   * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants}, then
   * an <code>IllegalArgumentException</code> is thrown.</p>
   *
   * <p>If <code>expression</code>, <code>source</code> or <code>returnType</code> is
   * <code>null</code>, then a <code>NullPointerException</code> is thrown.</p>
   *
   * @param expression The XPath expression.
   * @param source The input source of the document to evaluate over.
   * @param returnType The desired return type.
   * @return The <code>Object</code> that encapsulates the result of evaluating the expression.
   * @throws XPathExpressionException If expression cannot be evaluated.
   * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in
   * {@link XPathConstants}.
   * @throws NullPointerException If <code>expression</code>, <code>source</code> or
   * <code>returnType</code> is <code>null</code>.
   */
  public Object evaluate(
      String expression,
      InputSource source,
      QName returnType)
      throws XPathExpressionException;

  /**
   * <p>Evaluate an XPath expression in the context of the specified <code>InputSource</code> and
   * return the result as a <code>String</code>.</p>
   *
   * <p>This method calls {@link #evaluate(String expression, InputSource source, QName returnType)}
   * with a <code>returnType</code> of {@link XPathConstants#STRING}.</p>
   *
   * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item
   * evaluation, variable, function and QName resolution and return type conversion.</p>
   *
   * <p>If <code>expression</code> or <code>source</code> is <code>null</code>, then a
   * <code>NullPointerException</code> is thrown.</p>
   *
   * @param expression The XPath expression.
   * @param source The <code>InputSource</code> of the document to evaluate over.
   * @return The <code>String</code> that is the result of evaluating the expression and converting
   * the result to a <code>String</code>.
   * @throws XPathExpressionException If expression cannot be evaluated.
   * @throws NullPointerException If <code>expression</code> or <code>source</code> is
   * <code>null</code>.
   */
  public String evaluate(String expression, InputSource source)
      throws XPathExpressionException;
}
